Telemeter.



F., N.`JOHNSON.

TELEMETER.

APPLICATION FILED oc. 29. |914.

Patented Feb. 6, 1917.

2` SHEETS-SHEET l- A TTOR/VEYS man c F. N. JOHNSON.

TELEMETER.

APPLICATION FILED ocT. 29. 1914.

Lewglee.

A TTHIVEVS Patented Feb.6,1917.

2 SHEETSSHEET 2.

FRANK N. JOHNSON, OT? HOLLY GROVE, ARKANSAS.

TELEMETER.

Application led Detoner 29, 1914.

To all cli/tom it may concern.'

Be it known that I, FRANK N. Jonsson, a citizen of the United States,and a resident of Holly Grove; in the county of Monroe and State ofArkansas, have invented a new and Improved 'elemeter, ot which thefollowing is a full, clear, and exact description.

rlhis invention comprehends the provision oit' an improved telemeter ormeans for measuring distances and particularly those off considerablemagnitude with accuracy and precision. 4

The primary object of the invention is comprehended by the provision 'ofan instrument of the character named for making linear or distancemeasurements which permits the use of various optical systems or systemsof light'retlection in such a manner that when two images, eitherpartial or total, are reHected by means of mirrors or prisms into atelescope, sighting instrument, or directly into the eye and broughtinto coincidence to produce a clear image of the 'object viewedmonocularly or otherwise, tri` angles will be erected with a liporoperlycalibrated part of the instrument and with the object viewed in such amanner as to estabw lish a ratio permitting accurate determination ofthe distance to be measured.

Another and important object of the invention is comprehended in theprovision of an improvement in telemeters in which a portion of theinstrument suitably calibrated forms the' base of a triangle with theobject viewed so that by varying the angle of divergence between twoparts of the instr ment, of which the base is one, and marking off onthe base a distance calculated to approximate that of the distance fromthe telescope, sighting instrument or eye, a coincidence of reflectionis then eiected by sighting through the telescope o1 sighting instrumentby adjustment of the parts of the instrument to form the proper anglebetween the two, and such distances may be quickly and accurately readwithout necessitating complicated and lengthy calculations.

A still further and important object of the invention is to provide aninstrument oi the character named which is adapted for use in makinglinear measurements in such a manner that the advantage of a long baseconsistent with convenient manipulation of Specification of LettersPatent.

Patented Feb.. f5, i911?, serial no. scaaSi.

the instrument is provided, in which a minimum absorption et thereflected rays is acquired to secure the proper coincidence of thereflected rays, and to provide for the use oit the underlying principlesand struetural features in connection with an apparatus designed for useas a range finder for military purposes, as a surveyors .instrument intriangulation or generally as a distance gage without departing from thespirit f of the invention, as well as provide iter such calculationsthat due to the tact that func tions in small angles vary as .theirarcs, the error introduced by this assumption is rendered almostnegligible and. the accuracy of the instrument thereby assured.

Viith the above and other objects in view, the invention resides in thepeculiar combination and arrangement of parts to be hereinafter morefully described, illustrated and claimed, it being also an object toprovide a device which is simple in construction, durable and etlicientin operation and not likely to get out of working order.

Reference is to be had to the accompanying drawings forming a part ofthis speciication, in which similar characters of reference indicatecorresponding parts in all the views, and in which- Figure l is a planview of a telemetcr construction constituting the preferred form of myinvention;

Fig. 2 is a bottom view thereof with the telescope or sightinginstrument omitted;

Fig. 3 is a cross sectional view taken on the line 3h?, of Fig. l andenlarged relative thereto Fig. is a sectional view taken on the linele-ft of Fig. 3;

Fig. 5 is an enlarged detail sectional view of a spring acting memberused with the device illustrated in Figs. l and 2;

Fig. G is a diagrammatic view illustrating the method et calculating inaccordance with the principles of the invention;

Fig. 7 is a sectional view taken on the line 7 3? of Fig. 8;

Fig. 8 is a plan view of a further modified iorm oi the apparatus;

Fig. 9 is a rear edge view thereof;

Fig. 10 is a `longitudinalsectional view partly in elevation of a stillfurther modified form of the invention;

Fig. 1l is a plan view of another form ci the invention;

lll)

Fig. 12 is a rcar odge vieiv thereof.

Fig. 13 is a sectional vieiv taken on the line 13-13 of Fig. 11.

In carrying my invention into practice and illustrating the principlesinvolved in the measurement and calculation of distances, in Figs. 1 to5, inclusive, I have illustrated the preferred form of the inventionwhich comprises an upper long arm 10 to ivhich .is pivoted a loivershort arm 11 at a point distant or remote from one end of the arm 10,ivhile also pivoted to the arm 1() is an auxiliary arm 12, the auxiliaryarm being pivoted to the arm 10 at a point less remote from its end at Aon a line of the long axis of the arm 10 indicated by the line AWB. Thearm 11 is pivoted at the point Y G- on a line of the axis of the Yarm 10so that said arms, including` the auxiliary arm, are adapted to swing byeach other or on horizontal planes. The longitudinal edges 13 and 14 ofthe arms 10 and 11 vvhile not neces sarily perfectly straight must beapproximately even or in aliuement when the axes of the arms areparallel, that is, they must lie in the saine surface, or nearly so,parallel to the axis of a revolving reflector 15 which is fixed to theauxiliary arm 12 to move or pivot therewith at 450 to the long axis AHKthereof, While a reflector 1G is fixed to the arm 10 at its opposite endat an angle of 45 to the axial line A--B relative to which the reflector15 is adjustable.

in order to support the reflector 15 a holder 17 is provided, the samehaving angular channel-forming end portions 18 receiving the reflectorsor mirrors therein for angular adjustment by set screws 19 operating`through the opposed portions of the holder near the top and bottomthereof at each end so as to accurately adjust the reliecto at theproper angle While the reflector is supported upon inturned ends 2O atthe bottom of the holder. The holder for the reflector 16 is indicatedby the numeral 21 and is similar in construction to the holder 17 withthe exception that instead of being attached to the pivot connecting thearms 10 and 12 and moving With the latter, it is provided with anattaching portion 22 removably fixed to the arm 10 by screws orotherwise so as to remain rigid therewith at an angle of 450 to theaxial line A-B constituting the longaxis of the arm 10.

In a simpler form of my invention hereinafter described and illust 1atedby Figs. 8 and 9, the arm 11 is pivoted to arm 10 at A, and reflector 15is rigidly fixed thereto to move or pivot therewith through the same arcas that described by arm 11 when movedwith reference to arm 10,butbecause, as will be shown hereinafter, the invention involves thedetermining the length from the pivot A to a certain constant offsetmaintained be- -tWeen the axes of the arms pivoting at A,

Y straight, should he even or symmetrical with respect to the axes.Extreme accuracy with this respect is necessary, but such accuracy isdifficult of accomplishment.' The dilficulty is overcome in the firstmentioned or preferred form of the invention by the introduction of :amechanical contrivance of which the auxiliary armI 12 formsa part. Theedges of the arms are made parallel to their axes, including the edge 23of the auxiliary arm, so that by the pivotal connection of the parts theaxes of the long,r arms and of thc revolving reflector 15 and edge 23 ofthe auxiliary arm 12 can -be brought into the same pla-ne; then if arm11 he rotated thriguigli an angle. arm 12 and the revolving reflectorivill be rotated through a smaller anglea the free extremity K of theauxiliary arm 12 being kept alivays at a, point in the long axis G-H ofarm 11, the angles'and'their functions, if small, bearing a constantratio as Will be hereinafter shown and errors due to inaccuracy of theedges Will be decreased by this ratio. To assist in this the extremityof the auxiliary arm 12 from the point A to the point K is normallylrept in contact with a straight edge formed by the horizontal member ofan angular plate 2e fixed to the arm 11 beyond the pivot G. Thestraight' edge is in the axis G-H of the arm 11, and the extremity K ofthe auxiliary arm is maintained at all times in contact with thestraight edge as by means of a spring pressed detent 25. This detent issecured to the arm 11 atl the opposite side of the auxiliary armrelative to which the straight edge 2-1 is secured and comprisesprojections 30 to engage the opposite end of the barrel and prevent itsdisplacement.

In one system of light reflection employed in this invention, a pair ofreflectors or mirrors 31 and 32v are'supported intermediately of thelength of the instrument on the arm 10 or centrally of its long andshort axes, the mirror 31 facingthe mirror 15 but facing rearwardlyinstead of forwardly and being disposed at an angle of 450 to the shortand long axes of the arm, While the mirror 32 faces the mirror 16 and isother Wise similarly located except that the mirror 31 is supportedabove the mirror 32, or

socket member or sleeve 3 vice versa. These mirrors are supported inholders 33 similar in construction to the aforesaid holders except thatthey are onehal'f the height thereof and are secured in the arm 10 by anattaching part 34, while the respective holders are secured to eachother by overlapping wings 35, all of said connections being detachable.

The attaching part Sie carries a squared permitting removable attachmentand adjustment of a telescope or sighting instrument 37 toward or awayfrom the mirrors or reflectors 3l and 32 and with respect to the line ofintersection thereof, as by means of a clamp 38 removably attached tothe telescope and provided with a downuuirdly oflsct and angularly bentshank 39 which engages the socket member or sleeve and is capable ofadjustment therein by set screws 0. In this manner the rays olf lightfrom a distant point, as the point C in l* 6, through the mirrors l5 and1G at the points A and ll, can be brought into coincidence due to theinterception of the rays of light reflected, by the mirrors 3l and S2 sothat the upper halt of the rays are received on one mirror andthe lowerhalf on the other mirror in the torni ot partial images which, whenbrought into coincidence by adjustment of the arms one relative to theother in a manner to be hereinafter more fully described, and after thetelescope or sighting instrument has been so placed that the line ofcollimation therethrough is properly regulated, will unite and form oneimage when viewed monocularly.

ln order to angularly adjust the arms one with respect to the other andangu'larly move the mirrors to secure the proper co* incidence of thereflected rays or partial images, a slide el engages the two arms, saidslide preferably comprising a pair of plates pivotally connected asshown at e3 in the centers of the plates particularly with respect totheir transverse dimension, so that when the arms and the axes thereofare in alinement the pivot will be disposed in the plane of the axes ofthe arms but may be adjusted to remain in the plane of the axis G-H ofthe arm 1l. `llor this purpose the opposite edges of the plates are bentin angular directions, as shown at 44, said being first extendedupwardly and downwardly and then inwardly to overlie the bottom face ofthe arm 11 and the upper lace ot the arm l0, while the portion l5extends just slightly over the face of the arm l@ and carries aremovable plate i6 which is marked or scratched at its center as slownat e7 to Vprovide an indicator or siero et' a Vernier which co-'a ctswith a prope"ly graduated scale 48. longitudinally of i* t vernier isdisposed.

he arm l0 adjacent to the edge atwhich l Y Reiner/'ably secured to theangular ends of the plates lZ, as shown at all, are leaf springs the.saine being attached to the plates at their cent-ral portions and havingtheir free ends acting against the edges of the arms 10 and ll withequal tension to normally move the arms into. alinement vertically,while mounted in the 'opposed portions of the plates are removableclamping jaws 5l each having out-turned end portions 52 to preventdisplacement thereof and being acted on by a pair ot screws 53 so thatby adjusting the screws against the action of the springs, the arms maybe adj usted or moved out of alinement the proper distance constitutingthe deflection or variation ot the position oit one arm relative to theother in order to bring about a coincidence ietween images when viewedthrough the sighting' instrument. The adjustment is made slight and the:uljusting device slid. longitudinally of the arms to increase thedeflection of one arm with relation to the other, the plates being treeto revolre on the pivot as the pivot remains in the axis tde-ll of thearm ll and moves out oit the axis fr B of the arm l0. lt thus appearsthat' the sections are pivoted to move relatively so that the shiftingot the slide when adjusted in the manner described operates to move onesection on the other to automatically erect an angle or triangle on oneot the legs ot the triangle or base .termed by the graduated arm and thedistance set ott forms the other side or leg ot' the triangle.

ln ordcr'to 'facilitate the adjustment of the plate on the arms tosecure more accurate adjustment, a micrometer is provided, the sameconsisting of a second slide 5e which is slidable on the lower sectionor arm ll and adapted to be adjustably secured thereto by a set scr^w55, while an oppositely threaded adjusting bolt 5G connects the slide 5dto a depending portion 57 of the slide comprised bythe plates ln thismanner the bolt may be turned for the purpose of shitting the slides inopposite directions simultaneously while the set screw is loose or whensaid set screuT is acting to hold the slide against movement on the armll the adjusting slide will be shifted on the arm relative to the slide54.1 so that the adjustment or movements of the par us can be regulatedto a nicety. The scale i8 is placed or fixed parallel to the axis of thearm l0 with its Zero mark in aline ment and at right angles opposite tothe pivot point G in the axis A l so it is evident that for any positionoi' the slide the distance trom (l, as @ll-L in Fig. 2, to the normaldropped from the rivet to the axis of the arm, as L-l/l in Fig. 2, isequal to the distanceV from Zero to the inarlr or indicator 47, thisdistance being equal to frl inrllig. 6.

'a constant ratio, this ratio being ln Fig. 2, I indicates the point ofcontact of the extremity K of the auxiliary arm l2 with the straightedge 24, E-F indicates a line erected normal to A-B at a point E, Flying in the axisof A K produced and M lying in the axis G-H. G-L inFig. 2 is equal tc A-E and L-M equals E-F mullt will be shown indiscussing the simpler form of the invention hereinbefore referred toand illustrated in Fig. S, that if a sca-le be placed on arm l parallelto the axis A-B, with its zero mark in alinemcnt and at right anglesapnea by ai@ ma@ opposite to the pivotpoint A in axis A-B,

' and a slide adjusted to separate the lower edges of the arms by adistance E-F equal to one half the base line A-B times the ratio of aScale division t0 the unit of measure used, and coincidence of imagesthen effected by moving the indicator 47 of the slide to any point F,the distance to the object viewed can be read on the scale opposite thisindicator. Therefore, remem bei-ing that L G is always equal to E A andL M equal to E F times a ratio, if with this preferred type ofinstrument a scale be placed as specified, with its zero opposite pivotpoint G and the slide adjusted to ,separate the lower edges of the armsby a distance equal to one-half the base line times the ratio of a scaledivision to the unit of measure used times the ratio and coincidence ofimages then effected, the distance to the object viewed can be read onthe scale opposite to the mark 47.

Errors due to slight inaccuracies of the edges will be decreased by theratio by the use of the third or auxiliary arm arrangement. This ratiocan be fairly large so that if a distance of 50 be read, using atelemeter equipped with this auxiliary arm, the ratio TG- being 5, theerror resulting fromthis use will be less than 0.32

and if the distance be great the error will Y be negligible.

In Fig. 6, which illustrates the method of calculating. A*B representsthe base line of the instrument, with a mirror a-n fixed at B at 4-50 toA B, and a mirror m-m pivoted at A fixed at an angle of to A-F. Cindicates the distant object.

A-B-C and D*EV-A are similar triangles having constant bases A and D-EThe variable B-C equals the variable A-E times constant of theinstrument, the constant being A-B being the base of the triangle A-BCand E-D the base of the triangle D-E-A and corresponding to the offsetof the instument.

As shown in this figure the line A-D is Y movement of the mirror interms of distances of which length B-C is required, the distance B-C canbe readfrom the scale. Still, further it is evident that A-B' and E-Dmay be of any length andthat therefore any value may be chosen for theratio and hence any scale clvivided deciinally may be used, the ratiobeing fixed thereby.

The form of the invention shown in Figs.

'8 and 9 of the drawings illustrates a form of mechanical contrivancefor carrying out the operation above set forth, and in this form of theinvention the structure is the same with the exception that instead ofhaving arms of different lengths as are the arms l0 and l1,and employingan additional or auxiliary arm 12, upper and lower arms 58 and 59 ofequal lengths are employed and are pivotally connected as shown at 60with interposing spacing members. A U-shaped bracket 6l isyxed toV thelower arm and receives both arms there-between with its bight portion 62adjacent to the extremities vof the arms which are thus pivotallyconnected, the'upper arm being thus permitted to swing or pivot with.respect to the bracket and lower arm and having a rounded end portion63 permitting a wide range of adjustment. In this case a holder 64 isused in lieu of the holder 17 and is provided with an attaching portion65 by which it is removably secured rigid with the upper portion of thebracket at an angle of l5@ to the axis of the lower arm or of the twgarms when the sameare in alinement. Due to the fact that the arms areflat or relatively'lonfg and thin, they are made of Inatei-iaisinhciently rigid to hold them rectilinear and prevent sagging thereofin the center or they may be stifened in any preferred manner. Y Y

In this instance, the'light rays from the same sources C 'through themirrors at the points A and B can be brought into coincidence and iev-Eand E-F or Fig. 6 measured by means ot the mirrors arranged in themanner described in connection with Figs. l and 2 by receiving the raysreflected by the lower halt of one end mirror on one of the centralmirrors and the reilected lays 0i? the upper half of the other endmirror on the other central mirror at right angles from said reflectingmirrors, so that a partial im* of the object viewed is thereby formed ineach oi the central mirrors and the two partial .images thus formedbrought into coincidence by adjusting the arms to more the mirrorcarried by the holder 6l at the point fr, so as to imite and form oneimage when viewed monocularly as by means of the telescope, sightinginstrument or eye direct in the manner described. Furthermore, all therays from each end mirror can be received by two central mirrors orreflecting prism systems ditlierently arranged 'from the mandes il d andviewed binocularly, the tr-:o sf )tirate and identical images being thuspresented one to each eye, when the reflected rays Yiroln the endmirrors are brought into coincidence by revolution of the mirror at thepoint A, so that with a scale iXed par-l allel to the axis 1li-B of thearm 5S and having its Zero opposite at right angles to the pivot il, itis evident that for any posin tion of the slide the distance from to thenormal drop from the center of the rivet forming the pivot o1 the slideplates to the axis of the arm is equal to the distance rfrom Zero to thegraduation or scratch l?, and

tlii.- distance is A-E oiu Fig. 6, so that the distance E-C can beconveniently read.

is above explained, the slide is adjusted so that the center o't therivet forming the 'L-,fot ot" the plates brought to the plane oi' theaxis rif-lf ot the arm by adjust n screws 53 and particularly thescrews, and the center ot the pivot .f .ing set io a point distant lP-Fin Fig. 6 :trom tlmy plane olf the i nis rif-ll oit the arm by the upperscrews, the springs holding the parts in this position, but in order toinitially adjust the screws of the slide so that a distance le--li maybe oli, some point ot known distance is observed and the slide adjustedto bring the mark -lT thereof at the i, Yading of the scale conformingto that disA tuice and then elliecting a coincidence b v means of thescrews ot the slide so that any other tmice may be obtained by effectinga coincide or the images by shifting the side inn"c fly or outwardlyrelative to the pivot oi' .the arms and then reading the scale ormeasurement orf set.

Any optical systemiused in exist-ing telemeters to magnify the objectsViewed can be used with these telemeters and in addition with amonocular type of this instrument,

instead ot placing teiescope objectives between the end reflectors andcentral reflectors, both objective and ocular may be placed beyond thecentral reiiectors as hereinbetore shown, the rays suffering doublereflection before entering the telescope. there are not, as in existingtelemeters, wo partial images, one superimposed above the other, formedby the two central mirrors, ot prism systems, but two complete imagesor' the object viewed, and these images are indistinct and separateuntil the rays 'from the end mirrors are brought into coincidence byadjusting the revolving mirror and the images are thereby merged intoone clear distinct image. Furthermore, it is evident that one pair orreiiectors can be dispensed with in the telemeters above described. Reliectors 16 and 32 may be omitted, the telescope receiving on the onehall of its ol jcctive rciiected rays from the object viewed throughreflectors l5 and 3l, and on the other halt direct rays from the objectviewed, the base line being thereby changed; also, in this case, thearms need not extend beyond reflector 3l and the telescope. Furthermore,the length oi the long leg of the right triangle formed by the paths ofrays trom an object to the ends of a base line and then reflected intocoincidence with the base line as above described, is determined bvscaling the long leg of an auxiliary right triangle, as the triangleAME-F in Fig. 6, the angle of which included between the long sides isone-halt the angle included between the long sides ot the first triangleerected by the rays from the object to the arm of the implement a base.This second triangle is formed by the base line by an arm fixed rigidlyto one reflector, as the arm 59, and the slide which separates the armand the base line by a distance equal to one-halt the base line timesthe ratio ot one scale division to the unit ol2 masure ot the requireddistance so that the triangle is autinnatically erected in effectingcoincidence and the scale reading gives the required distance, because,as shown above, the long legs of the triangles bear a constant ratiowhen tlm adjacent angles are small.

From the above modilication oi' devices for carrying out or utilizingthe principles inif'olved, it will be seen that diil'crent arrangementsand different designs orf arms and slides from that shown and describedmar be made and used but the principles outlined tor the purpose oicil'ecting coincidence and determining distance are the same oressentially so. However, further modifications are shown, as torinstance, in Fig. l0. wherein the telemeter is shown as comprising atube or tubular arm (3G with the reiiectors inclosed or inca-sed in atube near each end thereof andoppositely disposed at angles @t 4,50 tothe optical axis or the tube, while the tube is pr vided with openings'ln this case, -1

CJ D

Cin

67 producing windows near its ends to admit light to the reflectors,while an eyepiece GS is provided for the central reflectors, thereflectors constituting a system of reflection or prism system beinglocated in any of the manners heretofore described. The view, which is alongitudinal or median section, is illustrated with the optical axis A-Bof the instrument at one side of the axis Y-Z of the tube, parallel toit and distant therefrom a distance equal to one-half the base linetimes the ratio of a scale division of the scale used, to the unit ofmeasure used. The reflector 15 is rigidly fixed to an outer tube G9which is of sufficient diameter to allow a space between the tubes andwhich is pivotcd to the inner tube at 70 so that when the tubes areparallel the optical axis A-B coincides or alines with the axis of theouter tube, the reflecting surface revolving about the pivot 70 whichlies in the optical axis A-B.

A, slide 71 also in the form of a tube and closely fitted to the tube G6is mounted on the latter and slit, as shown at 72, to avoid unduefriction between it and the tube on which it slides. The slide operatesin the space between the inner and outer tubes constituting` long andshort arms of the instrument and carries at its end, close to the pivot70, a collar 73 consisting of a ringthe inner surface of which iscylindrical and which exactly fits the slide, while its outer surface isspherical with a radius corresponding to the radius of the inner surfaceof the outer tube (S9, while the center of said spherical surface is thecenter of the transverse dimension of the ring. Thus, at any position ofthe ring the axes of the inner and outer tubes intersect at the centerof the ring at the point F because the axis of the inner tube is a locusof the center of the ring and the cylindrical surface of the outer tubeis tangential to the spherical surface of the ring about a great circle.In this manner the axis A-F of the outer tube G9` the optical axis A.-Band the distance E-l between these axes adjacent to the center of thering or collar are respectively AF, A--B and Ehi" of Fig. G, hence thedistance to the object viewed, coincidence having' been effected bymoving` the slide, may be read on a scale 69 placed on the tube 66 andusing the edge of the slide 71 as an indicator. The zero of the scalemustkbe opposite a point on the optical axis distant from the pivot 70the length of the slide, the length of the slide meaning the distancefrom the center of the collar to the indicator. In order to move theslide in the structure illustrated the inner tube is slotted,

`as shown at 74, and carries a rack 75 which is attached longitudinallyto the inner face thereof and engaged by a pinion 7 6 carried attheinner end of a shaft 77 having an exterior grasping portion which ispreferably knurled so that the shaft can be turned for' .rotating thepinion in engagement with the rack to shift the Slide on the inner tubeto varythe degree V`of divergence between the inner and outer tubes byshifting the collar.

It is to be understood that when the outer and inner tubes are parallel,the optical axis A-B of the inner tube coincides with the axis A-F ofthe outer tube, the movable refiector 15 being disposed at an angle ofi5@ to the optical axis. lllhen the collar V73 is shifted by movement ofthe Vslide,`the

eyepiece GS may carry the occular as commonlv done in existingtelemeters.

In the form of the invention illustrated in Figs. 11, 12 and 13 of thedrawings, the frame of the telemeter is of different construction butembodies or utilizes the same principles as that above described. Inthis form of the invention the device is shown as comprising atubulararm 7 8 constituting` the long arm of the instrument orappliance, the same carrying upon supports 79 the usual rigid reflectorswhile its axis A-B constitutes the base referred to inthe abovecalculations. A short arm 80 is pivotedV at one end to the arm 7S andcomprises a tube which is bent inward and downward at one extremity, asshown at 81, so that one end thereof fits in a socket 82 at the adjacentend of the arm 7 8, a. line passing through pivot A and parallel to thestraight part of arm S0 corresponding to A F. The arm 80 can thusrevolve about the pivot and carries the revolving reflector 15corresponding to the reflector' above described, and when the straightportion of the arm 80 is parallel to the axis AV-B of the arm 78, therefiector 15 will be disposed at an angle of 45O`to the axis A1-B, theaxis of the arms being always disposed in the same horizontal plane.

A slide S3 is mounted on the arms and comprises a pair of tubes S11 and85 which are preferably slit to avoid undue friction, and to the tube orsleeve Si a U-shaped plate 8G is fixed, the plate being bentv around thesleeve and extending tangentially to and beyond the sleeve 85. To thisplate the sleeve 85 is pivoted above and below its vertical axis, thepivots 87 thereof extending throufrh elongated openings S8 in the plateand being held in position by adjusting screws 89 operating in oppositedirections through angular portions 90 `oi" or carried by the plate. Bythese screws a distance equal to one-hall the base line times the ratioof the scale division of the scaleused to the unit of measure used maybe maintained between the axis fir-B of the arm 78 and a line passingthrough said axis at a point A constituting the pivot and parallel orotherwise with respect to the arm 80, the line passed and the distancebetween the same are respectively 5i-B, fr-lf and E-F of Fig. G, so thatthe distance of the object viewed can be read on a scale as above, thescale 80 being placed on the tubular arm 78 using an edg'e ofthe sleeveas an indicator with the zere of the scale placed ahead or back of thepoint A, depending upon which edge is used as an indiactor, by adistance equal to one-halt the length o1c the sleeve.

rillhe form of the invention illustrated in Figs. l to 8 and 1l to 12are adapted particularly for engineering work or surveying, while theform of the invention shown in Fig. lO is adapted particularly for navaland military uses, although there is no restriction to this particularuse and all forms may be used for the dierent purposes. In all existingtelemeters two telescope objectives are used, being placed between theend reflectors and the central reflectors, while a telescope eyepiece oroccular is placed entirely without the reflecting system. Two magnifiedpartial images of the object viewed are thereby received by the eye, theupper portions being reflected by the upper reflector and the lowerportions by the lower reflector. Coincidence is determined by making theupper partial image coincide with the lower partial image along a hori-Zontal line in the center of the field oit view. Thus, in looking at atree, if the instrument be not adjusted, the lower part oitx the treewould be seen to the right or lett of the upper part. Frein theforegoing description it is thought that the principles and operation ofthe device will readily appear and that further description will beunnecessary..

Having thus described my invention, what l claim as new and desire tosecure by Letters Patent is l. ln a telemeter, an arm constituting aside of a triangle formed with the object, a second arm piveted to thelirst arm, an auxiliary arm also pivoted to the lirst arm, a system oflight reection embodying rellecting members carried by the first arm andthe auxiliarv arm. the reflecting member l .7 i C;

cai ied by the auxiliary arm being adjustable with said arm to securecoincidence et the images et the object viewed, and means for angular-lyadjusting the second arm relative to the first arm at a given ratio, the

said second arm controlling the adjustment of said auxiliary arm and thereflecting member carried thereby, whereby the distance to the objectviewed can be ascertained.

2. device for ascertaining the distance betuleen a point and an objectviewed, comprising an arm constituting a side of a triangle formed withthe object, a second arm pivoted to the first arm and adjustablerelatively thereto at a given ratio, an auxiliary arm also pivotal tothe lirst arm, a stem oi light reflection embodying reflecting memberscarried by the lirst arm and the auxiliary arm, the rel'lecting membercarried by the auxiliary arm being adjustable with said arm to securecoincidence et the the object viewed, a slide cooperating with the iirstand second arms to angular-ly adjust the second arm relative to thefirst arm, the said second arm controlling the adjustment ci" saidauxiliary arm to cause a minute angular disalacement thereoil relativeto the second a rin.

3. A derice for ascertaining the distance between a point and an objectviewed, comprising an arm constituting a side of a tri- ;le formed withthe object, a second arm oted to the first arm and adjustable relativelythereto at a given ratio, an auxiliary arm also pivoted to the iirst armand adjusted angularlyv when the said second arm is adjusted, a systemof light renection embodying reflecting members carried by the first armand the auxiliary arm, the reliectine' member carried by the auxiliaryarm being capable of adjustment to secure coineidence of the images ofthe object viewed, a sighting instrument cooperating with the re.fleeting system, the first mentioned arm being provided with a scaledecimally divided, a slide embodying pivoted plates engaged with thelirst and second arms, means carried by the slide lor shitting the armstherein, whereby vwhen the slide is adjusted `longitudinally the pivotedarms will be augularly adjusted, whereby their angle oil divergence maybe varied, said slide having a marl: cooperating with the intlicatiousoi the scale, whereby when coincidence is obtained the distance may lemeasure(L on the scale.

el. A telemeter comprising an upper and a lower arm pivotally connected,a light refleeting system including reflecting meniers carried by thearms, the reflecting member carried by the lower arm being adapted tomore witi said. arm, a telescope tor receiving the reflected rays from adistant peint, a slide for varying the degree oit divergence between thearms as the slide is shifted, the said slide embodying a pair of platespivotally connected at their center the plates having their oppositeedges bent in angular direction to overlie the bottom face of the lowerarm and the upper face of the upper| arm, means carried by the slide forvarying the degree of divergence between the arms independent of themovement of' the slide, a scale extending longitudinally on the upperarm, and an indicator carried by the upper plate and adapted to coperatewith the scale to indicate the distance to be measured.

5. A telemeter comprising a pair of arms pivotally connected, a lightreflecting system including reflecting members carried by the arms, thereflecting member carried by one arm being movable therewith, atelescope for receiving the reflected rays from a distant point, a slideforY varying the degree of divergence between the arms as the slide isshifted, the said slide embodying a pair of plates pivotally connectedat their centers, the opposite edgesof said plates being bent 'inangular directions to overlie the bottom face ofI the lower arm and theupper face of the upper arm, means carried by the slide for varying thedegree of divergence between the arms independent of the movement of theslide, a second slide slidable on the lower arm, means connecting thesaid second slide with a depending arm on the first slide for adjustingthe slides relative to each other, a scale on the upper arm, the llrstslide being adapted to coperate with the scale to indicate the distanceto be measured when coincidence is effected.

6. 1n a telemeter, an upper and a lower arm pivotally connected, a lightreflecting system including reflecting members carried by said arms, thereflecting member carried by the lower arm being adapted to move withsaid arm, and a slide for varying the degree of divergence between thearms as the slide is shifted along the arms to secure coincidence of theimages of the objects viewed, the said slide comprising upper and lowerplates pivoted together at the center and having angular ends to overlapthe bottom face of the lower arm and the upper face of the upper arm, anindicator carried by the upper plate and extending over one edge of theupper arm, a scale arranged longitudinally on the upper arm adjacent oneedge and with which the said indicator cooperates, springs secured tothe angular' ends of the plates and engaging the edges of' the arms tonormally move the same into alinement, clamping aws mounted in theopposite portions of the plates and adapted to engage the opposite edgesof the arms, and means for adjusting the clamping jaws against theaction of the springs to move the arms out of alinemenrJ independent ofthe movement of the slide along the arms.

7. A device for ascertaining the distance between a point and an objectviewed, comprising pivoted arms, one arm of which constitutes the sideof a triangle formed with the object, a system of light reflectionembodying reflecting members carried bythe arms, one of said arms andthe reflecting member carried thereby being capable of adjustment tosecure coincidence of images of the objects viewed, a member pivoted tothe first arm and acting on said second arm to cause minute angulardisplacement thereof, means for causing greater angular displacement ofsaid member, said angular displacements or angles being of constantratio, and a scale for indicating the said angular displacements orangles in terms of distance.

8. A telemeter, comprising an arm constituting a side of a triangleformed with the object viewed, an auxiliary arm pivoted at one end tosaid first arm at a point adjacent one end of said arm, reflectingmembers carried by the said arms, the reflecting member carried by theauxiliary arm being at its pivoted end, and another arm pivoted to thefirst arm at a point more distant from its end than the pivot of theauxiliary arm and adapted to be displaced angularly relative to thefirst arm, the free extremity of thea uxiliary arm being engaged by thelast mentioned arm at a point adjacent its pive oted end, whereby thedisplacement of said arm relative to the first arm, causes a minuteangular displacement of the auxiliary arm and the reflector carriedthereby.

9. A telemeter, comprising an arm constituting a side of a triangleformed with the object viewed, a second arm pivoted to the first arm, anauxiliary arm pivoted at one end to the first arm adjacent one end ofthe latter, reflecting members carried by the first arm and theauxiliary arm, the'rellecting member carried by the auxiliary arm beingcapable of adjustment with said'arm to secure coincidence of the imagesof the object viewed, said second arm being pivoted to the first arm ata greater distance from its end than the pivot of the auxiliary arm andcapable of being displaced angularly relative to the first arm, the freeend of the auxiliary arm extending a short distance beyond the pivotedend of said second arm, means for holding the free end of the auxiliaryarm in engagement with said secondV arm, and means Jfor displacing thesaid second arm relative to the first arm to cause a minute angulardisplacement of the auxiliary arm and its reflector.

l0. A telemeter comprising two arms pi votally connected, a lightreflecting system including reflecting members carried by the arms, thereflecting member carried by one arm being adapted to move with said armto secure coincidence of the images of the object Viewed, a slide forvarying the degree of Vdivergence between the arms as theslide isshifted, the said slide embodying a pair of plates pivotally connectedat their cen-V ters, the plates having their opposite edges ico arrangedto engage the said arms, Ineens carried by the slide foi' varying thedegree o1 divergence between the arms independent of the movement of theslide, a scale on one in testimony whereof I have signed my naine tothis specification 1n the presence of two subserlblng Witnesses.

FRANK N. JOHNSON.

of said arms, and an indicator carried by Witnesses: one of seid platesand eoperatng with the H. B. COOK, seele to indicate the distance to bemeasured. V. O. WELLS.

Copies of this patent may be obtained for :ive cents each, by addressingthe Commissioner of IPatents,

, Washington, D. C.

